1. Field of the Invention
This invention relates to gas generators and is particularly directed to solid propellant gas generators for producing pure nitrogen gas at temperatures above 2200.degree. K in the complete absence of other gaseous products and metallic vapors.
2. Description of the Prior Art
Several solid propellant gas generators exist which are capable of producing warm, pure nitrogen gas. The majority of these gas generators are based upon alkali azides [sodium azide (NaN.sub.3), potassium azide (KN.sub.3), or lithium azide (LiN.sub.3)]. The basic concept is to react the alkali azide with a fuel which leaves a solid residue and yields pure nitrogen gas. A typical example from U.S. Pat. No. 3,833,423 is: ##STR1## Recent developements in gas dynamic lasers have indicated that when a source of hot nitrogen gas (T&gt;2200.degree. K) is mixed with cold carbon dioxide and water vapor, superior performance is obtained when compared to a system in which all the gases (N.sub.2, CO.sub.2 and H.sub.2 O) are produced in the hot state.
The state-of-the-art warm nitrogen generators are limited to the temperature range 1775 to 1960.degree. K, the boiling points of the alkali halides (fluorides, and chlorides). The performance of a gas dynamic laser is severely degraded if volatile alkali metal atoms or alkali halide molecules are entrapped in the flowing gas stream.
U.S. Pat. No. 3,947,300 describes a warm nitrogen generator based upon the reaction: EQU M(N.sub.3).sub.x + M(NO.sub.3).sub.y + SIO.sub.2 .fwdarw. Silicate Residue + N.sub.2
where M = Na, K, Ca; x and y = 1 or 2
The basic concept of this reaction is to form a silicate glasslike residue and free nitrogen gas. However, thermochemical calculations indicate substantial portions of the silicate residue will begin to dissociate at temperatures above 2200.degree. K yielding gaseous atoms of Na and K.
U.S. Pat. No. 3,814,694 suggests the utilization of calcium nitrate (Ca(NO.sub.3).sub.2) in conjunction with a variety of reducing agents. However, large quantities of water vapor are generated in addition to nitrogen gas which would be very detrimental to the operation of a gas dynamic laser.
It is obvious that any compound containing an alkali metal atom cannot be used in a system where the flame temperature will exceed 2200.degree. K.